1. Field of the Invention
The present invention relates to a protective, diffusive film and more particularly to a protective, diffusive film which can suppress the formation of burrs at the time of processing for the formation of sheet-like films, possesses excellent punchability, and is excellent in handleability in a sheet-like film form, a process for producing the same, and a surface light source device and a liquid crystal display device using said protective, diffusive film.
2. Background Art
A large number of surface light source devices provided with a protective, diffusive film have hitherto been proposed. An example of a surface light source device using a protective, diffusive film 110 is shown in FIG. 5. FIG. 5 is a cross-sectional view of a liquid crystal display device 135 provided with a surface light source device 120 which is an edge-type flat light source. The surface light source device 120 comprises, for example, a light source 121, a light guide plate 122, a reflection film 124, a light diffusive film 125, a lens film 140, and a protective, diffusive film 110.
The light guide plate 122 is surface light projection means, and has a light source 121 on its side end and, on its non-light-outgoing surface remote from a light outgoing surface 122a, a dot pattern 123 for diffusing light from the light source 121 and directing the light to a light outgoing direction. The reflection film 124 is provided on the non-light-outgoing surface side of the light guide plate 122 and functions to block off unnecessary light beams and, at the same time, to reflect and return light beams to a predetermined direction.
A lens film 140 is disposed on the light outgoing surface 122a side of the light guide plate 122 through a light diffusive film.(a diffusive plate) 125 for diffusing light to conceal the dot pattern 123 in such a manner that the lens film 140 on its prism surface 140a faces the light outgoing surface side.
In order to impart the function of diffusing light to the light diffusive film (diffusive plate) 125, the light diffusive film (diffusive plate) 125 has hitherto been formed by incorporating, in a dispersed state, organic or inorganic beads as a light diffusing agent into a transparent resin substrate, or by coating an ink containing organic or inorganic beads as a diffusing agent onto a transparent resin substrate.
A protective, diffusive film 110 is provided on the light outgoing surface side of the lens film 140, for preventing the prism 140a in the lens film 140 and a liquid crystal display element 133 from coming into direct contact and being damaged by each other, for example, due to vibration in transit. The protective, diffusive film 110 also has the function of slightly diffusing light for concealing stripes of the prism 140a in the lens film 140, a spacer (not shown), and the like. To this end, the protective, diffusive film 110 has hitherto been formed by incorporating, in a dispersed state, organic or inorganic beads as a light diffusing agent into a transparent resin substrate, or by coating an ink containing organic or inorganic beads as a diffusing agent onto a transparent resin substrate.
A transmission liquid crystal display element 133 comprising a liquid crystal layer 130 sandwiched between a lower substrate 132 and an upper substrate 131 is provided on the light outgoing side of the surface light source device 120, and the liquid crystal display element 133 is illuminated from backside by the surface light source device 120.
The conventional protective, diffusive film 110 is mounted on a surface light source device (backlight) after sheet punching. When the punchability is poor, burrs are formed on the end face of the product and adversely affect the function of the surface light source device.